I've had items just disappear out of the game and I had an entire shelter disappear. Things don't seem to be saving like they should.

I harvested like 5 64-blocks of wood and put them in a chest and they all disappeared. This happened like 3 or 4 times in a row. I made changes to my storage chests, thinking that there was just too much data in one area and none of the changes saved.

I deleted the whole world and started with a new one. I stayed in the default texture pack, thinking that maybe the other texture pack was bugged. I built an entire shelter with furnace, chest and craft table. I saved and left the game for a few minutes. When I came back, none of the work had saved.